The present invention has for its object a knife provided with a blade which can automatically retract as soon as said blade is no longer in contact with the object to be cut.
A knife generally comprises a casing in which a blade can slide, fixed to a blade carrier, which can have two positions, a first so-called extended position, in which the blade projects outside the casing, and a second so-called retracted position, in which the blade is disposed integrally within the casing.
In a simple modification, the blade carrier moves in a slideway provided in the casing, and comprises notches which permit holding said blade carrier, and hence the blade, in a predetermined position.
This modification is not satisfactory from a standpoint of safety, because the blade remains in the extended position, risking causing harm, if the user does not think to retract it after use.
A first improvement consists in providing at the level of the blade carrier return means to the retracted position. In this case, the blade carrier comprises a finger piece adapted to be moved by the thumb of the user so as to cause the blade to extend or to hold the blade in extended position. Thus, as soon as the user releases the finger piece, the return means automatically return the blade to the retracted position.
Even if this improved version provides greater safety than the simple version, it remains no less dangerous at the time of the end of cutting, the instant when the greatest number of accidents occur.
Thus, to cut an object with a knife, the user must exert a relatively great force in the direction of the object to be cut, and give a cutting movement to the knife directed toward himself. Also, at the end of cutting, at the time at which the knife ceases to be in contact with the object, control of the knife can escape the user, so that the knife, and more particularly the blade, can come into contact with a portion of the body of the user and cut him, unless he has had the reflex to release the finger piece so that the blade retracts.
The present invention seeks to overcome the drawbacks of knives of the prior art by providing a reliable and secure knife, provided with a blade which retracts automatically as soon as said blade is no longer in contact with the object to be cut.
To this end, the invention has for its object a knife comprising a casing and a blade which can have two positions, a first so-called extended position, in which the blade projects outside the casing, and a second so-called retracted position, in which the blade is disposed integrally within the casing, characterized in that it comprises a blade carrier to which is connected the blade, a housing on which is slidably mounted said blade carrier removably mounted within the casing, and a finger piece-pusher mounted slidably on the casing so as to move said blade carrier forwardly thereby to place the blade in the cutting position, said blade carrier and finger piece-pusher being returned to the retracted or rest position, by return springs, and in that means are provided to secure the finger piece-pusher and the blade carrier together to place the blade in said first position, said means being uncoupled by the conjoint action of rotation and extraction of the blade carrier relative to the finger piece-pusher, following the cutting action.
According to one embodiment, said disconnectable means are constituted by a drive finger secured to said finger piece-pusher, whose end is provided with a notch for receiving a projection secured to the blade carrier, said notch and projection being laterally offset in the rest or retracted position of the finger piece and the blade carrier, placed in alignment and in engagement upon the beginning of movement of the finger piece-pusher and uncoupled as soon as the blade is in the course of cutting, such that said notch will no longer be on the return path of the projection during retraction of the blade carrier.
There is thus obtained a knife with a truly safe retractable blade in the sense that the blade is already placed in automatic retraction position, as soon as traction is exerted on the knife to carry out a cut, the retraction taking place automatically as soon as the blade leaves or escapes from the object or element which has been cut, without having to exert any action on the finger piece-pusher.